Electrical attachment plug



Dec.1, 1942. w v L. LU-DWIG 2,303,483

ELECTRICAL ATTACHMENT PLUG Filed Feb. 4, 1941 Iig.1.

, INVENTOR.

LULIIELUDLd/E BY W Patented Dec. 1, 1942 3 i UNITED STATES PATENT OFFICE ELECTRICAL ATTACHMENT PLUG Louis Ludwig, Brooklyn, N. Y.

Application February 4, 1941, Serial No. 377,375

6 Claims.

This invention relates generally to electrical plugs and more particularly to electrical attachment plugs of the round prong type.

At the present time in the United States, the most universally used type of connector for low voltage, residential and similar use, is the flat prong type. For certain specialized uses here and for general use in a large number of foreign countries, an electric service outlet or receptacle is used in which the female socket portions thereof are adapted to receive plug prongs which are rod like or cylindrical in external configuration.

Plugs having rod like pins or prongs which are adapted for use with such sockets are known, and principally take the form of a plurality of separate rod like prongs, mounted upon a body or cap composed of insulating material. In order to increase the resiliencyv of such prongs, they are provided with a central diametrically arranged slot which extends down the prong from the outer end thereof and bifurcates the same. The lower portion of the prong is usually threaded and carries nuts thereon for making a connection with the wire conductor or the lower portion of the prong is attached to a separate base carrying wire connection means thereon. Plugs constructed in this manner have several disadvantages, as to cost of production and as to utility. As usually constructed, the rod like prong is manufactured from rod stock on a screw machine and requires, as a separate operation, the slitting thereof, which is usually performed by milling or sawing.

When in use, by reason of the construction thereof, the prong does not make contact with the socket element into which it is placed over a sufiicient area so that a relatively high resistance contact is made. Another disadvantage of such construction lies in the fact that the insertion of the plug into the socket is diflicult by reason of inadequate and improper movement of the prong parts.

It is a principal object of the present invention to produce a novel electrical attachment plug in which the plug prongs have a generally rod like external configuration and yet, in which many of the disadvantages inherent in prior constructions are overcome.

Among the objects of the present invention, lies the provision of an electrical attachment plug of the class described in which the prong members are fabricated from sheet material so that the same may be blanked and formed by pressing operations. Such construction permits of large scale production at relatively lowered costs, accompanied by a superior performance.

Another object herein lies in the provision of an electrical attachment plug of the class described in which the rod like prongs are integral with the electrical conductor or wire contact members thereof.

Another object herein lies in the provision of electrical attachment plug prong structure which not only provides for a lower resistance connection with the feed wire attached thereto, but also results in higher conductivity being maintained between the prong and the female receptacle therefor.

A still further object herein lies in the provision of an electrical attachment plug of the class described in which the manual insertion or removal of the plug prongs from the female receptacles in the socket therefor is made easier and more convenient.

A feature of the present invention lies in the fact that plug prongs having rod like external configuration are so mounted with relation to the base members therefor, that the prongs may flex within desirable limits toward or away from each other to accommodate certain variations in the inter-receptacle spacing in the sockets with which the plug may be normally used.

These objects and other incidental ends and advantages will more fully appear in the progress of this disclosure and be pointed out in the appended claims.

In the drawing forming a material part hereof, similar reference characters designate corresponding parts throughout the several views, in which:

Figure 1 is an elevational view, partly in section, showing a preferred embodiment of the invention. The portion of the figure shown in section is such as may be seen from the plane ll on Figure 2.

Figure 2 is a top plan view of Figure 1.

Figure 3 is an enlarged plan view of a blank from which is fabricated one of the contact elements.

Figure 4 is an elevational view partly broken away showing one of the contact elements.

Figure 5 is an end elevational view partly broken away of one of the contact elements as might be seen from the right hand side of Figure 4.

Figure 6 is a diagrammatic horizontal sectional view taken generally on the plane 6-45 of Figure 5.

Figure 7 is a diagrammatic horizontal sectional view taken generally on the plane l-l of Figure 4.

shown in the other figures.

Figure 8 is a diagrammatic horizontal sectional view taken similarly to Figure 6 but showing an old construction for purposes of comparison.

In accordance with the invention, the electrical attachment plug as a unitary device is generally indicated by numeral 20. The plug 20 comprises generally the contact elements 2| and 22 and the body or cap element 23.

The body or cap elements 23 may be of any usual construction well known in the art and is preferably fabricated by moulding the same from insulating material such as Bakelite or rubber.

The cap includes an orifice 48 through which may enter the conductors or wires 49 and 50. The cap 23 includes a platform upon which the base members 30 and 3| are mounted as will be more particularly described hereinbelow. Since the cap element is otherwise of usual construction, a further detailed description thereof is considered unnecessary. The contact elements 2| and 22 are preferably of identical construction and, therefore, a detailed description of thecontact element 2| will suffice for both.

The contact element 2| is preferably blanked and formed from a sheet of resilient electrical conducting material. In the construction of successfully operated plugs in accordance with the present invention, the applicant has utilized as a sheet material that known as quarter hard brass, sg of an inch thick. In forming the element 2|, it is desirable that the grain of .the metal run longitudinally of the blankrseen in Figure 3. For the purpose of clarity, the parts of the contact element 2| as shown in the plane blank form in Figure 3 are given singly primed reference characters corresponding to the parts As seen in Figure 3, the blank includes the outside edges 33 and 34, the end edges 35' and 35' and the central or first slot 32'. .As seen in Figure 3, the portions of the material disposed above the dot-dash line 52', subsequently form the spring prong or con tact member 24. The portion of the blank seen on Figure 3 below the dot-dash line 53 subsequently forms the basemember 30. The external configuration of the base member 38 is generally governed by the the internal configuration of the flange 54 and the platform 5| of the cap 23. The base member 30 is provided with a contact screw hole 4| which is preferably internally threaded, 3

and a boss hole 46'. The lug 42 performs its usual function of maintaining the wire 49 in proper position with relation to the screw 39.

A preferred method of forming up the contact portions 26' and '21 is by cupping the same so that as seen in Figure 3, the plane exposed surface of each of the contact portions 26 and 21 becomes concave. Subsequently, the two halves of the contact member are bent toward'each other away from a longitudinal axis bisecting the slot edges 33 and 34 are preferably spaced from each other a distance equal to the parallel and spaced edges of the slot 32. The rounded ends 31 and 38 produce the effect of a hemispherical slotted outer end on the contact member 24.

In assembling a plug utilizing two of the contact members just described, the platform 5| of the cap 23 may have moulded therein a pair of bosses 44 and 45. Contact elements 2| and 22 may be placed over these bosses and the bosses swaged over. The bosses penetrate orifices corresponding to the orifice 46'. Obviously, other means may be used for attaching the base members 30 and 3| to the platform 5|. The contact screws 39 and 43 are engaged in the orifices correspondin to the orifice 4| and said orifices may have been previously downwardly extruded for the purpose of providing a greater thread 4 bearing area. The bosses 44 and 45. together with the internal surface of the flange 54 serve to properly position the bases 3|] and 3|, and

hence the other parts integral thereto.

The finished plug will then include the contact members 24 and having the contact portions 25, 21, 28 and 29 and the lugs 42 and 43.

Numerals 36 and 35 indicate the opposed end edges of the contact members 26 and 2'! respectively.

Operation It will thus be seen that I have provided a novel attachment plug which, by reason of the resilient nature of the parts and the particular configuration thereof, is capable of a greatly improved and advantageous operation. Since the contact elements 2| and 22 are connected to the bases there of and 3| respectively, each by a single bend 47 and 57 respectively, contact elements 2| and '22 may move toward or away from each other within certain limits about the axis which is substantially the same as the axis of said bends.

Since the axes of these bends are not tangential to the circumference of the flange 54, this resilient movement of the contact elements toward or away from each other, together .with a slight axial rotation of the plug 20 will permit accommodation to sockets having inter-receptacle spacing varying within certain limits.

By reason of the slot which extends entirely up one side of the prong across the end and down a considerable distance on the side, the two halves or contact portions 26 and 21 or 28 and 29 may move toward. or away from each other to accommodate socket receptacle diameters of different values. While an action generally similar thereto occurs in the posts or prongs of solid. slotted construction as indicated by the dot-dash lines in Figure 8, the resiliency of applicants contact members is increased by the fact that they are hollow.

This hollow or curved inner surface construction of applicant's contact elements 2| and 22 permits not only the movement of the contact members 24, 25, or 26, 21, toward or away from each other, but also permits a constriction of the parts so that the total efiective diameter not only perpendicularly to the slot, but in any other diametrical direction as well, may be reduced so that contact element may conform to a receptacle having cylindrical construction of circular cross section, less than the uncompressed contact element.

In the old construction illustrated in Figure 8, maximum resistance is encountered when inserting the plug at the tip or end of the prong, whereas in the present construction, the insertion of the prong offers a minimum of physical resistance at the entering point because where the "slot 32 ends, maximum pressure is reached and the entire contact element can be compressed or constricted about a vertical axis.

This condition exists throughout the entire length of the contact elements and the action by the lower portion thereof is illustrated in the schematic section shown in Figure 7 in which the dot-dash lines show the altered position of the parts under peripheral pressure. In applicants plug, the contact elements tend to make a cylindrical contact of high conductivity as contrasted with the old construction which tends to make a circumferential linear contact of low conductivity,

I Wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

I claim:

1. An electrical attachment plug comprising: a cap element; a contact element composed of a single sheet of conducting material, including a contact member and a base member; said contact member having the longitudinal outer edges thereof bent toward each other, said outer edges being oppositely disposed and spaced from each other, forming a hollow cylinder having a slot, a rounded top and an open bottom; said base member having a greater length than the width thereof and being connected at one end thereof to the inner end of said contact member; said base member being positioned substantially at right angles to said contact member and extending under the open bottom of the cylinder and under said slot.

2. An electrical attachment plug comprising: a cap element; a contact element composed of a single sheet of conducting material, including a contact member and a base member; said contact member having the longitudinal outer edges thereof bent toward each other, said outer edges being oppositely disposed and spaced from each other, forming a hollow cylinder having a slot. a rounded top and an open bottom; said base member having a greater length than the width thereof and being connected at one end thereof to the inner end of said contact member; said base member being bent substantially at right angles to said contact member and extending under the open bottom of the cylinder and under said slot; said base member being secured to said cap.

3. An electrical attachment plug comprising: a cap element, a contact element composed of a single sheet of conducting material, including a contact member and a base member; said contact member having the longitudinal outer edges thereof bent toward each other, said outer edges being oppositely disposed and spaced from each other, forming a hollow cylinder having a slot, a rounded top and an open bottom; said base member having a greater length than the width thereof and being connected at one end thereof to the inner end of said contact member; said base member being bent substantially at right angles to said contact member and extending under the open bottom of the cylinder and under said slot; said base member being provided With an orifice, a means penetrating said orifice and securing said base member to said cap.

4. An electrical attachment plug comprising; a cap element; a contact element composed of a single sheet of conducting material, including a contact member and a base member; said contact member having the longitudinal outer edges thereof bent toward each other, said outer edges being oppositely disposed and spaced from each other, forming a hollow cylinder having a slot, a rounded top and an open bottom; said base member and its corresponding contact member being joined by a bend; said bend being disposed at an acute angle with relation to an imaginary radius extending from the center of said cap element and passing through said contact member; said base member being disposed substantially at right angles to said contact member and extending under the open bottom of the cylinder and under said slot; said base member being fixedly secured to said cap.

5. An electrical attachment plug comprising: a cap element; a pair of contact elements each composed of a single sheet of conducting material including a contact member and a base member; each of said contact members having the longitudinal outer edges thereof bent toward each other, said outer edges being oppositely disposed and spaced from each other, forming a hollow cylinder having a slot, a rounded top and an open bottom; each base member and its corresponding contact member being interconnected by a bend; said bend being disposed at an acute angle to an imaginary line passing through both of said contact members; each of said base members being disposed substantially at right angles to its corresponding contact member and extending under the open bottom of the cylinder and slot of its corresponding contact member; said base members being secured to said cap.

6. An electrical attachment plug comprising: a cap element; a pair of contact elements each composed of a single sheet of conducting material including a contact member and a base member; each of said contact members having the longitudinal outer edges thereof bent toward each other; said outer edges being oppositely disposed and spaced from each other, forming a hollow cylinder having a slot, a rounded top and an open bottom; each base member and its corresponding contact member being interconnected by a bend; said bend being disposed at an angle less than a right angle to an imaginary line passing through both of said contact members; each of said base members being disposed substantially at right angles to its corresponding contact member and extending under the open bottom of the cylinder and slot of its corresponding contact member; said base members being secured to said cap.

LOUIS LUDWIG. 

